This invention relates to a ligature tool for applying small elastic ligatures onto orthodontic brackets without patient discomfort, and in particular, to a ligature tool to automatically pick up one ligature at a time, expand it over a tip and snap it onto the bracket.
Orthodontists move teeth by applying low level forces over long periods of time. Brackets are directly bonded to the teeth and a force is applied to the tooth by an arch wire which passes through a slot in each bracket. The arch wire is held in the slot of the bracket with an elastic ligature (O-ring) and extends from bracket to bracket. The brackets are often of different sizes and shapes, depending on the size and position of the individual teeth. The ligatures are generally replaced once or twice a month when the arch wires are adjusted or changed as the teeth move.
Presently, the elastic ligatures are usually applied by a hemostat. Orthodontists and their assistants have become very skilled in using the hemostat and are surprisingly fast in picking up a ligature and stretching it around the bracket. However, this requires concentration and eye movement from the pick-up point to the mouth. Patients with sensitive teeth experience discomfort as the ligature is stretched around the bracket. In addition, to add to the discomfort, teeth undergoing orthodontic treatment are often sore and sensitive to pressure.
The American Orthodontic company has sold a simple "U" shaped tool called a "Speedo Plastic Ligature Director" for applying the ligatures. The ligature is pre-loaded onto the "Speedo" with a hemostat and then rolled off the "Speedo" onto the bracket. Using the "Speedo" reduces the discomfort to the patient but does not save time overall. Both the hemostat and the "Speedo" are simple, inexpensive and easily sterilized.
U.S. Pat. No. 4,277,236 is directed to a ligature tool which automatically picks up the first ligature and applies the ligature without applying pressure to a patient's bracket. While this patent may have the advantages of the present ligature tool, the patented tool is far more mechanically difficult to operate.
U.S. Pat. Nos. 4,040,187 and 4,472,137 disclose ligature tools of general interest, however they do not pick up the first ligature and they do apply pressure against the bracket.
It is the principle object of this invention to provide a ligature tool which picks up the first ligature and transfers it to a bracket without applying pressure to the tooth.
Another object is to provide a ligature tool that is mechanically simple to operate.
Another object is to provide a ligature tool that has a tip (pre-loaded with a plurality of ligatures) that is easily replaced.